Peugeot BB104 tuning advice needed

Hello, I have recently acquired a non-variated 1963 BB104. It appears to be completely stock. My plan is to let my daughter use it to get to high school in the fall. The issue that I have is that we have hills and the moped struggles mightily to overcome them. It came with 13x42 gearing which I have changed to 13x43. This helped a bit but requires a good running start and no red lights to get over the hill. I have a 45 but that may be too low. Also, I’ve probably lost 3-4 mph off the top end.

The carb is the original Gurtner D10 and the muffler is original except I opened up the pinch in the outlet nub. I would like to keep it on the quiet side. It has been suggested I try

a Dellorto 15:15 in place of the Gurtner. I would be fine with low to mid performance over top end speed.

Any additional advice or ideas would be appreciated. Thanks in advance.

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Re: Peugeot BB104 tuning advice needed

That thing is cool. Not sure how big the gurtner is but probably sufficient. Id hack on a little circuit pipe, surprisingly not that loud even wo a baffle. And if u adventurous do a little porting.

Re: Peugeot BB104 tuning advice needed

what kind of top speed are you getting out of it?

the exhaust might have a removable baffle under the end cap that might help. carb and intake restriction are going to be bottle necks, but if it was mine, I wouldn't go nuts with the mods.

absolutely make sure your ignition timing is spot on, if it is late, might seem ok on the flat, but you will die on the hills and starts.

and check your compression. using a high quality oil at the right mix can help ring sealing / compression / power, along with lubrication. the thing is 60 years old.

I have a '64 and it slows enough on big hills (like probably any stock single speed) to need to pedal it.

Re: Peugeot BB104 tuning advice needed

cool bike! Definitely swap the carb and maybe intake if needed, the carb provides a bigger boost for sure, non-variated bikes and hills don't really mesh too well stock

Re: Peugeot BB104 tuning advice needed

Hey guys, thanks for the response. The Gurtner is 9mm/11mm is measured at intake side and air box side of Venturi. The top speed with the original sprocket was about 28-30 speedometer indicated and I lost 3-4 with gearing change. The exhaust has a plate near the rear with a tube running through it that has 6 1/8 holes in it to allow the exhaust to empty into a smaller space with the exhaust

tip in it. I have not done anything to the air box or filter screens. I can take pictures for the curious. I am unfamiliar with circuit pipe. I’ll Google. Thanks again.

Re: Peugeot BB104 tuning advice needed

Re: Peugeot BB104 tuning advice needed

Hah. Thanks Pat Splat

Re: Peugeot BB104 tuning advice needed

Kevin Borcheld /

Exhaustport is al already get rid of carbon?

And how much mm is the squish? Maybe you can install a thinner headgasket and/or sanding the head down on a glasplate with sandingpaper (in dutch “afvlakken”)

0,8 mm squish is safe

Re: Peugeot BB104 tuning advice needed

Thanks Kevin, I don’t want to do any internal modifications at this time. It is running well except climbing hills. I’ll do some exhaust and carburation mods first.

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